<?php
/**
 * Locale API: WP_Locale_Switcher class
 *
 * @package WordPress
 * @subpackage i18n
 * @since 4.7.0
 */

/**
 * Core class used for switching locales.
 *
 * @since 4.7.0
 */
#[AllowDynamicProperties]
class WP_Locale_Switcher {
    /**
     * Locale switching stack.
     *
     * @since 6.2.0
     * @var array
     */
    private $stack = array();

    /**
     * Original locale.
     *
     * @since 4.7.0
     * @var string
     */
    private $original_locale;

    /**
     * Holds all available languages.
     *
     * @since 4.7.0
     * @var string[] An array of language codes (file names without the .mo extension).
     */
    private $available_languages;

    /**
     * Constructor.
     *
     * Stores the original locale as well as a list of all available languages.
     *
     * @since 4.7.0
     */
    public function __construct() {
        $this->original_locale     = determine_locale();
        $this->available_languages = array_merge( array( 'en_US' ), get_available_languages() );
    }

    /**
     * Initializes the locale switcher.
     *
     * Hooks into the {@see 'locale'} and {@see 'determine_locale'} filters
     * to change the locale on the fly.
     *
     * @since 4.7.0
     */
    public function init() {
        add_filter( 'locale', array( $this, 'filter_locale' ) );
        add_filter( 'determine_locale', array( $this, 'filter_locale' ) );
    }

    /**
     * Switches the translations according to the given locale.
     *
     * @since 4.7.0
     *
     * @param string    $locale  The locale to switch to.
     * @param int|false $user_id Optional. User ID as context. Default false.
     * @return bool True on success, false on failure.
     */
    public function switch_to_locale( $locale, $user_id = false ) {
        $current_locale = determine_locale();
        if ( $current_locale === $locale ) {
            return false;
        }

        if ( ! in_array( $locale, $this->available_languages, true ) ) {
            return false;
        }

        $this->stack[] = array( $locale, $user_id );

        $this->change_locale( $locale );

        /**
         * Fires when the locale is switched.
         *
         * @since 4.7.0
         * @since 6.2.0 The `$user_id` parameter was added.
         *
         * @param string    $locale  The new locale.
         * @param false|int $user_id User ID for context if available.
         */
        do_action( 'switch_locale', $locale, $user_id );

        return true;
    }

    /**
     * Switches the translations according to the given user's locale.
     *
     * @since 6.2.0
     *
     * @param int $user_id User ID.
     * @return bool True on success, false on failure.
     */
    public function switch_to_user_locale( $user_id ) {
        $locale = get_user_locale( $user_id );
        return $this->switch_to_locale( $locale, $user_id );
    }

    /**
     * Restores the translations according to the previous locale.
     *
     * @since 4.7.0
     *
     * @return string|false Locale on success, false on failure.
     */
    public function restore_previous_locale() {
        $previous_locale = array_pop( $this->stack );

        if ( null === $previous_locale ) {
            // The stack is empty, bail.
            return false;
        }

        $entry  = end( $this->stack );
        $locale = is_array( $entry ) ? $entry[0] : false;

        if ( ! $locale ) {
            // There's nothing left in the stack: go back to the original locale.
            $locale = $this->original_locale;
        }

        $this->change_locale( $locale );

        /**
         * Fires when the locale is restored to the previous one.
         *
         * @since 4.7.0
         *
         * @param string $locale          The new locale.
         * @param string $previous_locale The previous locale.
         */
        do_action( 'restore_previous_locale', $locale, $previous_locale[0] );

        return $locale;
    }

    /**
     * Restores the translations according to the original locale.
     *
     * @since 4.7.0
     *
     * @return string|false Locale on success, false on failure.
     */
    public function restore_current_locale() {
        if ( empty( $this->stack ) ) {
            return false;
        }

        $this->stack = array( array( $this->original_locale, false ) );

        return $this->restore_previous_locale();
    }

    /**
     * Whether switch_to_locale() is in effect.
     *
     * @since 4.7.0
     *
     * @return bool True if the locale has been switched, false otherwise.
     */
    public function is_switched() {
        return ! empty( $this->stack );
    }

    /**
     * Returns the locale currently switched to.
     *
     * @since 6.2.0
     *
     * @return string|false Locale if the locale has been switched, false otherwise.
     */
    public function get_switched_locale() {
        $entry = end( $this->stack );

        if ( $entry ) {
            return $entry[0];
        }

        return false;
    }

    /**
     * Returns the user ID related to the currently switched locale.
     *
     * @since 6.2.0
     *
     * @return int|false User ID if set and if the locale has been switched, false otherwise.
     */
    public function get_switched_user_id() {
        $entry = end( $this->stack );

        if ( $entry ) {
            return $entry[1];
        }

        return false;
    }

    /**
     * Filters the locale of the WordPress installation.
     *
     * @since 4.7.0
     *
     * @param string $locale The locale of the WordPress installation.
     * @return string The locale currently being switched to.
     */
    public function filter_locale( $locale ) {
        $switched_locale = $this->get_switched_locale();

        if ( $switched_locale ) {
            return $switched_locale;
        }

        return $locale;
    }

    /**
     * Load translations for a given locale.
     *
     * When switching to a locale, translations for this locale must be loaded from scratch.
     *
     * @since 4.7.0
     *
     * @global Mo[] $l10n An array of all currently loaded text domains.
     *
     * @param string $locale The locale to load translations for.
     */
    private function load_translations( $locale ) {
        global $l10n;

        $domains = $l10n ? array_keys( $l10n ) : array();

        load_default_textdomain( $locale );

        foreach ( $domains as $domain ) {
            // The default text domain is handled by `load_default_textdomain()`.
            if ( 'default' === $domain ) {
                continue;
            }

            /*
             * Unload current text domain but allow them to be reloaded
             * after switching back or to another locale.
             */
            unload_textdomain( $domain, true );
            get_translations_for_domain( $domain );
        }
    }

    /**
     * Changes the site's locale to the given one.
     *
     * Loads the translations, changes the global `$wp_locale` object and updates
     * all post type labels.
     *
     * @since 4.7.0
     *
     * @global WP_Locale $wp_locale WordPress date and time locale object.
     * @global PHPMailer\PHPMailer\PHPMailer $phpmailer
     *
     * @param string $locale The locale to change to.
     */
    private function change_locale( $locale ) {
        global $wp_locale, $phpmailer;

        $this->load_translations( $locale );

        $wp_locale = new WP_Locale();

        WP_Translation_Controller::get_instance()->set_locale( $locale );

        if ( $phpmailer instanceof WP_PHPMailer ) {
            $phpmailer->setLanguage();
        }

        /**
         * Fires when the locale is switched to or restored.
         *
         * @since 4.7.0
         *
         * @param string $locale The new locale.
         */
        do_action( 'change_locale', $locale );
    }
}